Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on well logging, profiling and monitoring of well conditions throughout the productive life of the well. With the most accurate and up to date information available, a considerable amount of time and money may be saved in managing production from the well. Similarly, over the years, added emphasis has been placed on other time saving measures such as performing well applications with as few a number of physical interventions as practical. For example, in many situations a series of related applications may be run by way of a single deployment of a toolstring into the well as opposed to several separate deployments of individual application tools into the well.
One such opportunity for reducing the number of well interventions is in the area of well stimulation. As used herein, the term “well stimulation” is meant to refer to fracturing, gravel packing, or any number of well treatment applications directed at stimulating a formation reservoir in order to encourage and maintain hydrocarbon recovery therefrom. For example, in many circumstances a cased well may be present with a perforated production region at the reservoir. That is to say, openings or perforations may traverse the casing and extend into the surrounding formation reservoir. However, in order to optimize hydrocarbon recovery from the reservoir, stimulation applications may be carried out at the region. Indeed, as noted below, multiple stimulation application procedures may be carried out at the region with a single trip in the well of a properly configured toolstring. As such, the time required for multiple deployments of different application tools to the region may be condensed into a single ‘stimulation’ trip, saving countless hours and capital expenditures.
As indicated, a toolstring may be configured to carry out multiple related stimulation applications near a perforated region of a cased well. For example, the same toolstring may be equipped to carry out a fracturing application, followed by a gravel packing application and hydrocarbon recovery upon a single delivery of the toolstring to the site of the perforated region. More specifically, a fracturing application may be applied where a proppant containing slurry is directed from a release mechanism of the toolstring toward the noted perforations. In this manner, the perforations may be stimulated and propped open.
A subsequent circulation of a gravel packing slurry may be directed from the same release mechanism or elsewhere toward the noted screen mechanism and exposed portions of the formation (i.e. in the area of the perforations). As such, the formation may be supported and the screen mechanism tightly secured in place. In this manner, reliable hydrocarbon recovery may proceed through the porous gravel pack occupying the space between the screen mechanism and the perforated region. Furthermore, fracturing, gravel packing, and production through the screen mechanism may all be achieved through a single deployment of the toolstring. Indeed, in certain situations, the toolstring may even be equipped with a perforating gun so as to allow formation of the perforations in advance of the described stimulating applications. That is to say, even perforating may be achieved as part of the single toolstring deployment.
Unfortunately, while the above described stimulation techniques may be cost effectively employed on a single trip in a cased well, they may be ineffective altogether when such a toolstring is delivered to an open-hole well. Unlike a cased well, an open-hole well may include a variety of exposed formation layers, some of which may hinder effective recovery through a screen mechanism, even where fracturing and/or gravel packing has been employed at the production region. That is, as in the exemplary circumstance below, conditions at formation layers outside of the production region may have an impact on recovery due to the open-hole nature of the well.
Often times, hydrocarbon recovery efforts are directed at oilfield formations that are primarily alternating layers of sand and shale. The thin sand layers in particular, may be good candidates for perforating, fracturing, and hydrocarbon recovery. By the same token, the predominantly shale makeup of the formation layers may allow the well to remain un-cased without undue concern over its structural soundness for follow-on applications. Thus, the cost of casing the well may be saved.
Unfortunately, even a properly positioned screen mechanism at the thin sand layer is subject to water and other contaminants emanating from other surrounding layers such as the shale layers. In the case of water contamination, hydrocarbon production through the screen may be rendered ineffective. Additionally, with no casing, the gravel slurry or other treatment material can have a substantial, negative effect on the surrounding wellbore wall of the open hole well. Thus, as a practical matter, fracturing, gravel packing and follow-on hydrocarbon recovery are not pursued via use of a single toolstring employed on a single trip in an open-hole well.